Micro- and nano-CT scanners are increasingly used in precision engineering. Proper selection of the key components of these devices allows elimination of most artifacts already during data acquisition. Typical nano-CT scanners contain an air bearing rotary stage for object manipulation due to their rotational accuracy compared with conventional bearings. In this work, the radial error motion of such an air bearing rotary stage is reduced to 3 nm by optimising the feeding system, leading to a new state of the art record for passive aerostatic bearings to our knowledge.